A modified classification of the family Asclepiadaceae R. Br. s.s. into three tribes – Secamoneae, Asclepiadeae s.l. and Stapelieae s.l. – is proposed. The position of attachment of the caudicles to the pollinia is suggested as a criterion for defining the erect and pendulous stature of the pollinaria. The concept of the transverse stature of pollinaria has been abandoned. In addition to the stature of the pollinaria, the morphology of the anther sacs (whether or not embedded in the tissue of the anther wings) and the position of anther wings with respect to the anther sacs are suggested as supplementary characters for tribal classification of the family. The characters of the gynoecium, particularly the presence or absence of true styles and the sharp constriction between stigma‐head and ovaries (i.e. clavuncular morphology) have also been suggested as useful in differentiating Asclepiadeae s.l. and Stapelieae s.l, along with the stature of the pollinaria. The circumscription of Asclepiadeae is emended to accommodate taxa of the former tribe Gonolobeae as a subtribe. The circumscription of Stapelieae has been retained in a wider sense, as suggested by Decaisne (1844). The tribes Fockeeae Kunze, Liede & Meve (1994), Marsdenieae Benth. (1876), Ceropegieae Benth. (1876), and Stapelieae s.s. sensu Benth. (1876; non Decne., 1844) have been relegated to subtribe status in the tribe Stapelieae Decne. (1844). Homology of the different parts of the gynoecium in the Asclepiadeae (s.l.) with those in the Stapelieae (s.l.) has been drawn. Segments of the style have been distinguished into ‘true style’ and ‘pseudostyle’, the former as parts of the ovary segment in development, the latter as stigma segment in development. The genus Tybphora R. Br. which was formerly treated under Stapelieae Decne. has been transferred to Asclepiadeae based on the morphology of the pollinaria, gynoecium and seed coat architecture.
Heterostemma Wight & Arn. (Asclepiadaceae) and a new species from India. Heterostemma vasudemni Swarupanandan & Mangaly, a new species belonging to Asclepiadaceae is described and illustrated. The discoid‐urceoloate corolla and the staminal coronal scales with a ventral appendage show this species to be intermediate between the two genera Heterostemma and Oianthus. Basically, the concepts of the two genera differ only in a pair of characters which, in the light of the new species seem not to be particularly diagnostic. On this basis it is proposed to merge the two genera together, by reducing Oianthus as a section under Heterostemma. Consequently, three new combinations are proposed. Examination of recent collections extends the distribution of what was 0. decanense, earlier considered to be endemic to Maharashtra, further south to Kerala.
The foliar theory of the stem, the application of which has been restricted to the pteridophytes, is now extended to the spermatophytes and the vasculature of the primary stem is viewed as a sympodium of foliar traces. Several new terms have been coined for the description of the primary vasculature; these include terms for vascular reticula and sympodia and two new conventions, the interleaf articulation ratio and interleaf articulation spacing. The patterns of primary vasculature in 20 Chenopodiaceous taxa have been re-described using a synoptic descriptive style. Based on the primary vasculature, within the Chenopodiaceae, two clear-cut groups have been recognized: (1) a Trioid vascular group, with 3-traced leaves and a median composite double trace, or taxa having such an ancestry; and (2) a Monoid vascular group, comprising taxa with 1-traced leaves and a composite double trace, or with this ancestry. The first group comprises the tribes Beteae , Chenopodieae , Atripliceae and probably the Polycnemeae and Corispermeae . The second group comprises the tribes Salsoleae , Suaedeae , Salicornieae and Camphorosmeae . In both the groups, reticulate and open vasculature are found, the latter being the derived state; the open vasculature derived from 3-traced ancestry is found to be different from that derived from 1-traced ancestry. These two groups differ from the subfam. Chenopodioideae ( Cyclolobeae ) and Salsoloideae ( Spirolobeae ), the groups identified on the basis of the cycloid/spiroid embryonic types. They match well with the groups identified from the chloroplast DNA analysis and appear to have distinct adaptive strategies; the first with modified/accrescent bracts, and the second with modified/accrescent perianth lobes. The findings from the primary vasculature therefore support the re-circumscription of the two subfamilies Chenopodioideae and Salsoloideae and the transfer of the tribes Camphorosmeae and Salicornieae to Salsoloideae . The processes involved in the diversification of primary vasculature in the Chenopodiaceae have been: changes from spiral to opposite phyllotaxy, reduction in the number of vertical rows of leaves, closed to open vasculature, non-storied to storied reticula, asymmetric to symmetric reticula, change in the loci of vascular articulations from the contributory arms to terminal arm of the composite trace, and wedgedsagittate to entire-acute base of reticula. Development of open vasculature from closed vasculature probably took place several times and followed independent lines. Therefore, many tribes in the family may be paraphyletic. Evolution of distichous sympodia from monostichous sympodia and vice versa, as proposed by earlier authors have been refuted. Strong correspondence of inference emerging from analysis of chloroplast DNA and primary vasculature refutes the probability of a protostelic origin of the eustele. It is argued that an atactostelic condition might have been ancestral, which gave rise to the protostelic condition on the one hand, and on the other to the eu...
SUMMARYSome anatomical details of branch abscission in Lagerstroemia microcarpa Wight (Lythraceae) are discussed. Repeated abscission of numerous annual twigs and subsequent healing of their scars produce irregular growth of the subjacent branch portions to give gall-like structures. In the abscission zone, secondary xylem fibres are thin walled and poorly lignified, with dense protoplasmic contents and closely spaced septa. Disintegration of pith parenchyma cells and shrinkage of bark and wood tissues contribute towards weakening of abscission zone. The protective zone situated proximal to the abscission zone is strongly lignified and rich m extractives. Detachment occurs immediately above the protective zone leaving the encircling dormant buds intact. Abscission scars are healed centripetally by the usual method of callus formation from the cambial tissue. It appears that branch abscission in L. microcarpa is a mechanism to withstand drought by reducing the transpiring surface.
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